Electrical devices, electronic devices, and communication devices have recently been significantly developed. These devices today are likely to utilize frequencies in a higher frequency band. Typically, these devices include various flexible printed circuit boards. The flexible printed circuit boards are therefore also desired to have properties including excellent electrical properties suited for frequencies in high frequency bands, and excellent heat resistance enough to withstand soldering.
Known materials for flexible printed circuit boards include, for example, a metal-polyimide complex that has excellent adhesion to metal foil and does not cause a decrease in the glass transition temperature, an increase in the coefficient of linear thermal expansion, an increase in the coefficient of hygroscopic expansion, or an increase in elastic modulus; and a polyimide resin and a polyamic acid vanish composition which can give such a metal-polyimide complex (for example, Patent Literature 1).